In a conventional storage type water heater, heated water is stored in a tank. On demand, hot water is withdrawn through an outlet in the upper end of the tank and cold water is simultaneously introduced into the lower end of the tank. During standby periods, when there is no water flow, there can be a loss of heated water through the inlet or outlet fittings due to convection. With rising energy costs, the standby heat loss through the service fittings can be a substantial economic factor.